Studies of Esterase-6 in DROSOPHILA MELANOGASTER. II. the Genetics and Frequency Distributions of Naturally Occurring Variants Studied by Electrophoretic and Heat Stability Criteria

Measurements of the electrophoretic mobility and thermostability of esterase-6 allozymes have been used to determine the amount of allelic variation at the esterase-6 locus in Drosophila melanogaster. We studied 398 homozygous lines obtained from four natural populations. Use of a spectrophotometric assay for esterase-6 activity has allowed precise quantitation of heat-stability variants. Using these methods, eight putative alleles were detected within the two most common electrophoretic classes. Analyses of F1 and F2 progeny show that the behavior of stability variants is consistent with the hypothesis that this variation is due to allelic variation at the Est-6 locus. Analyses of the gene-frequency distributions within and between populations show (1) that observed allele-frequency distributions do not deviate significantly from those expected for neutral variants, and (2) that there is little evidence for an increase in apparent divergence of the different populations at the genotypic or phenotypic levels when the additional variation detected is considered. These findings suggest that gene-frequency analysis alone is unlikely to resolve the question of the selective significance of allozyme variation.     

Protein polymorphism in native goats from central Argentina

Under the name of Creole goats, individuals of various origins, morphological and productivity characters are grouped. To characterize the genetic pool of goats from different sources in central Argentina, protein polymorphism revealed by electrophoresis was analyzed. A total of 109 adult animals from Santa Marı́a, Colón and Ischilı́n Districts, Córdoba Province, were studied. The red cells lysates were subjected to starch gel electrophoresis and specific staining procedures to reveal the activity of different enzymes and hemoglobin. Separation of plasmatic proteins was carried out by electrophoresis in polyacrylamide gel and stained with Coomassie Blue. From a total of 14 loci analyzed, eight were polymorphic in at least one flock. Four codominant alleles were detected in the locus βHemoglobin (βHb); three alleles in malic enzyme (Me), glucose 6 phosphate dehydrogenase (G6pdh) and lactate dehydrogenase (Ldh) and two alleles in catalase (Cat), transferrin (Tf), esterase-2 (Es-2) and phosphoglucomutase (Pgm). In all the cases, the observed genotype frequencies were not significantly different from those expected from Hardy–Weinberg equilibrium. The proportion of polymorphic loci (P%) varied between 21.4% and 42.9% and mean heterozygosity (H), between 0.061 and 0.117. Alleles at loci Cat, Me and Es-2 showed significantly different frequencies according to the sample origin. The flock from Colón District presented the highest levels of polymorphism. This is the only stock which includes hybrids of varying grade between Creole stocks and male specimens from Saanen and Nubian breeds.     

Enzyme polymorphism in Drosophila melanogaster populations in Iraq

Electrophoretic studies of the degree and pattern of polymorphism at two third-chromosome loci, esterase-6 (Est-6) and phosphoglucomutase (PGM), were carried out in three Drosophila melanogaster populations collected from different localities in Iraq: Mosul, Tuwaitha, and Basrah. The results show that only the Tuwaitha population was polymorphic for both loci; the other two populations were polymorphic for Est-6 and monomorphic for PGM. The allele frequency changes at both loci were followed for 20 generations in an experimental cage derived from the Tuwaitha population; it was found that there is a deviation from Hardy-Weinberg equilibrium at both loci toward the homozygote.     

Apparent Selection of Enzyme Alleles in Laboratory Populations of Drosophila

Twelve laboratory populations of recently collected Drosophila willistoni were begun with different frequencies of alleles at three enzyme loci, six populations at 25 degrees and six at 19 degrees . Periodic sampling of the populations allowed monitoring of the frequency changes in allozymes over time.-At Lap-5 (a locus coding for leucine amino peptidase), three alleles converged to the same frequencies in all populations at both temperatures. The apparent equilibrium frequency of the major allele was about.75; this is different from the frequency (.57) found in the natural population from which the experimental populations were begun. Allele frequency changes at the esterase-5 locus (Est-5) were slower but consistent in all cages. It is difficult to determine if an equilibrium has been reached. However, the frequency of the rare allele in all cages is about the same as in wild populations, 5%. Alleles at both Lap-5 and Est-5 are non-randomly associated with inversions in the chromosomes onto which they map. Because of these associations, it is impossible to unambiguously attribute the change in allele frequencies to selection at the loci being observed.-After one year, no significant gene frequency changes were detected at Est-7, the third locus studied.     

Genetics of esterases in Drosophila. III. Influence of different chromosomes on esterase pattern in Drosophila

The present report presents the results of starch and polyacrylamide gel electrophoretic studies of the influence of the X chromosome on the expression of esterase-6 in D. melanogaster × D. simulans hybrids heterozygous for locus Est-6 as well as studies of the influence of autosomes on esterase expression in Drosophila of the virilis group. A differential expression of esterase-6 has been detected in D. melanogaster × D. simulans hybrid males. A differential decrease in the activity of esterase-6 (both F and S allozymes) derived from D. melanogaster has been noted. In hybrid females, the activity of parental esterases is the same. It is suggested that the X chromosome regulates the expression of esterase-6 in D. melanogaster. Analysis of individuals obtained in different schemes of crosses between different species of Drosophila of the virilis group by use of stocks marked with mutations in various chromosomes indicates that other autosomes (in particular, autosomes 4 and 5) also influence the phenotypic expression of esterases (which are controlled by genes located on the second chromosome).     

PCR primers for polymorphic microsatellite loci in the desert locust,Schistocerca gregaria (Orthoptera: Acrididae)

Nine pairs of polymerase chain reaction (PCR) primers that amplify polymorphic microsatellite loci in the desert locust, Schistocerca gregaria (Forskal), were developed using a magnetic bead‐based enrichment protocol. A sample of 48 locusts collected during the 1993 and 1995 upsurge periods in Eritrea, East Africa, were genotyped. The number of alleles per locus ranged from six to 20; the average was 12.67. Allelic distributions were significantly different between samples from different localities.     

Identification, Inheritance, and Variation of Microsatellite Markers in the Black Scallop Mimachlamys varia

Five polymorphic microsatellite loci were identified in the black scallop Mimachlamys varia after construction of a genomic library enriched for (GT)n. To examine the transmission pattern of microsatellite alleles, several families were created and genotypes scored for three loci. The expected Mendelian ratios were found in 12 of 14 segregations examined. Unexpected segregations may be explained by a genotyping error (allelic dropout), given that when a specific allele was treated as dominant, the phenotypic ratios conformed to Mendelian expectations. The five loci were also examined in two samples from the Spanish coast. The two localities displayed similar mean values for the number of alleles per locus (7.2-8.4), allelic richness (7.2-7.9), and observed (0.389-0.484) and expected heterozygosity (0.545-0.618). Significant Hardy-Weinberg deviations were observed at three loci, with heterozygote deficiency occurring in all cases. Global multilocus θ value and allele frequencies at one locus revealed significant differentiation between the two localities.     

Genetic diversity of sharpnose mullet <Emphasis Type="Italic">Liza saliens</Emphasis> introduced in southern Caspian Sea in comparison with one native Aegean Sea population

Sharpnose mullet, Liza saliens (Risso, 1810) is one of the valuable species in Caspian shoreline and it was first introduced to Caspian Sea from Black Sea between 1930 and 1934. In the present study, we used six microsatellite markers to obtain genetic information for L. saliens from four localities of southern Caspian Sea and for one native population from Greece coastline (northern Aegean Sea). Results showed lower number of alleles (Na = 5.7–6) and higher observed heterozygosity (Ho = 0.74–0.83) in Caspian Sea samples, related to the native Aegean population (Na = 8, Ho = 0.68). Significant deviations from Hardy-Weinberg expectations were detected in 19 out of 28 tests. Low genetic differentiation (provided Fst values) among samples was detected, but Behshahr sample was significantly differentiated from all the others. The UPGMA tree revealed three major clusters: the Behshahr sample and Greek population were clustered in two different clades, and the remaining three samples formed another cluster. The low genetic variation and spatial differentiation among Caspian Sea samples may be justified by the recent establishment.     

Gene Differences between the Sex Ratio and Standard Gene Arrangements of the X Chromosome in DROSOPHILA PERSIMILIS

The sibling species Drosophila pseudoobscura and D. persimilis each carry two gene arrangements in the right arm of the X chromosome; Standard (ST) and Sex Ratio (SR). The SR sequence of D. persimilis and the ST sequence of D. pseudoobscura have the same banding pattern. These cytologically identical arrangements carry different alleles at the esterase-5 (Est-5) and phosphoglucomutase-1 ( Pgm-1) loci. All the alleles on the SR arrangement of D. persimilis are also present on the ST arrangement of that species, and the same allele was most common in all cases. However, the allele frequencies at the Pgm-1 locus are significantly different between the two arrangements. Within the ST arrangement of D. persimilis, the alleles at the Est-5 and Pgm-1 loci are in linkage equilibrium.     

Further Evidence for Selective Differences between Isoalleles in Drosophila

A number of separate strains of Drosophila pseudoobscura were inbred for 38 generations of brother-sister mating with forced heterozygosity for two alleles of either the octanol dehydrogenase or esterase-5 locus. Crosses were set up within each of these inbred lines such that simple mendelian ratios were expected, and eggs from these crosses were placed on media with additions of simple chemicals likely to interact with alleles of the two loci—octanol and ethanol for the ODH locus and tributyrin and triacetin for the E-5 locus. Similar crosses were set up involving parental flies with normally heterozygous genetic background as a control.—Significant deviations from mendelian expectation were observed in inbred E-5 flies grown on tributyrin, inbred ODH males grown on octanol, and inbred ODH females grown on ethanol. There was also a strong effect of octanol medium on males of one of the inbred E-5 lines, and a weak effect of tributyrin medium on ODH inbred females.—The probability that these results reflect interactions between these loci and the environment is assessed in the light of differences between the present results and those obtained at earlier stages of inbreeding.     

Frequency Distribution of Esterase-5 Alleles in Two Populations of DROSOPHILA PSEUDOOBSCURA

Statistical tests comparing allele frequencies in natural populations with those predicted by various theories of genic variation depend critically on the accurate enumeration of alleles. This study used a series of five sequential electrophoretic conditions to characterize the allele frequency distributions of esterase-5 in two large population samples of Drosophila pseudoobscura from California. In Standard chromosome lines 12 electromorphs were discriminated using a single electrophoretic condition. When four additional criteria were used, the number of electromorphs increased to 41, 33 in one population and 22 in the other. Both populations had the same two alleles in high frequency, with other alleles present in frequencies of 6% or less. Although each population had a number of unique alleles, a χ² contingency test demonstrated no significant genetic divergence between them. A statistical comparison of allele frequencies in both populations with that predicted by neutral models suggests that the individual and combined distributions deviate from neutrality in the direction of purifying selection.—Sex-Ratio chromosomes differed markedly from Standard chromosomes in both allelic content and diversity. In 32 Sex-Ratio chromosomes from one population only three alleles were found, all of which were detected under the initial "standard" electrophoretic conditions. Moreover, none of these alleles was found in the Standard chromosome lines.     

An Assessment of "Hidden" Heterogeneity within Electromorphs at Three Enzyme Loci in Deer Mice

Allelic heterogeneity within protein electromorphs at three loci was examined in populations of deer mice (Peromyscus maniculatus) collected from five localities across North America. We used a variety of electrophoretic techniques (including several starch and acrylamide conditions, gel-sieving, and isoelectric focusing) plus heat denaturation. Of particular interest was the supernatant glutamate oxalate transaminase system (GOT-1; aspartate aminotransferase-1 of some authors), which under standard electrophoretic conditions had been shown to exhibit basically a two-allele polymorphism throughout the range of maniculatus. The use of all of the above techniques failed to uncover any additional variation for GOT-1 in these populations. Similarly, no new scorable variation was resolved at the essentially monomorphic malate dehydrogenase-1 locus by additional conditions of electrophoresis. In marked contrast to the results for the above two enzymes, the use of multiple conditions of electrophoresis resolved the 8 standard-condition electromorphs of esterase-1 into a total of 23 variants showing strong geographic differentiation in frequency. These 23 electromorphs were further divided into a total of 35 variants by thermal stability studies. However, the allelic nature of all of the thermal stability esterase variants remains to be documented. The results of this study, taken together with the remarkable geographic heterogeneity for this species in ecology, morphology, karyotype and mitochondrial DNA sequence, suggest that some form of balancing selection may be acting to maintain the GOT-1 polymorphism.     

A Comparative Study of the Esterase-5 Locus in DROSOPHILA PSEUDOOBSCURA,D. PERSIMILIS and D. MIRANDA

Electrophoretic phenotypes of the esterase-5 locus were examined in the sibling species D. pseudoobscura, D. persimilis and D. miranda. D. persimilis alleles were found to have uniformly higher charge on monomers than corresponding alleles of either D. pseudoobscura or D. miranda. Consequently, D. persimilis shares no alleles in common with either D. pseudoobscura or D. miranda, while the latter two species share a number of alleles. It was discovered that by increasing the concentration of acrylamide gel and increasing the length of migration, more allelic differences could be distinguished. Also more alleles were discovered by examining monomer mobility in addition to dimer mobility. In D. persimilis and D. miranda it was found that the previously known high frequency allelic classes broke down into several allelic classes. A test of goodness-of-fit to the infinite alleles model was done and a rough agreement with the model was found.     

Phosphoglucose isomerase polymorphism in the shrimp Metapenaeus affinis

Three phenotypes of phosphoglucose isomerase (PGI) were detected in abdominal muscle extracts from the shrimp (Metapenaeus affinis) by starch-gel electrophoresis. The observed phenotypes were assumed to be under the control of two allelic genes. This assumption was supported by the observed distribution of phenotypes. There were no significant differences in the distribution of PGI phenotypes among samples of shrimp taken from Basrah waters, Iraq and from Kuwaiti waters, Arab Gulf. The three PGI alleles observed in M. affinis appear to be the same in the two localities.     

Development and characterization of nine polymorphic microsatellite markers in the Chilean kelp Lessonia nigrescens

A total of nine microsatellite loci were isolated and characterized in the Chilean kelp Lessonia nigrescens Bory. Using two different enriched libraries, we observed 1-14 alleles per locus in two samples of 21 kelp individuals each. The observed heterozygosities ranged from 0.05 to 0.80 and all loci are in Hardy-Weinberg equilibrium for one or both samples. Seventeen samples collected from different sites showed high allele diversity along the species distribution. The variation detected at these markers is currently being used for the study of populations of Lessonia nigrescens at different geographical scales.     

Development and characterization of microsatellite markers for Liporrhopalum tentacularis Grandi,the pollinator fig wasp of Ficus montana Blume

Microsatellite markers for the pollinator fig wasp Liporrhopalum tentacularis were developed using genomic libraries enriched for di‐, tri‐ and tetranucleotide repeats. A subset of 31 positive clones was sequenced and primers were designed. Eleven primer pairs produced polymorphic amplification products in L. tentacularis. Eight markers gave unambiguously scorable patterns and were further characterized on 29 individuals collected from different fruits of the dioecious host fig Ficus montana in Indonesia. Three to 19 alleles per locus were detected in this set of samples. The observed heterozygosity ranged between 0.10 and 0.55.     

Nearly identical allelic distributions of xanthine dehydrogenase in two populations of Drosophila pseudoobscura

In a previous study, Keith (1983) showed by sequential gel electrophoresis of the esterase-5 protein in Drosophila pseudoobscura that a highly polymorphic locus with many alleles can have very similar frequency distributions in populations separated by 500 km. The present work studies another highly polymorphic locus, xanthine dehydrogenase, in the same California population samples, using the same technique to distinguish allelic classes. Twelve electromorphs were found in one population and 15 in the other. Both populations shared a single very frequent (approximately 60%) allele, as well as five other alleles in low but similar frequencies. In addition, each population had an array of unique alleles present only once in one population sample but absent in the other. A statistical test against the stationary distribution for neutral alleles shows that, if the populations are at equilibrium, then purifying selection is operating on xanthine dehydrogenase. The extremely close similarity in frequency distributions of the alleles between populations for both the xanthine dehydrogenase and esterase-5 loci, despite differences in allele frequency distribution between loci, strongly emphasizes the importance of migration in influencing genic diversity in these populations.     

Esterase-7, a common constituent of numerous mouse tissues.

1. Electrophoretic and staining techniques for the relatively specific demonstration of esterase-7 in mouse tissues are described. Esterase-7 was found to be a common constituent of most mouse tissues. 2. The electrophoretic polymorphisms determined by three alleles a, b and c were studied in nine mouse strains. 3. The banding pattern of esterase-7 is being described and the isoelectric points of the allelic bands are being estimated. 4. Recombination studies on a further 129 animals confirmed that the Es-7 locus is tightly linked to Es-2 and Es-11. 5. Esterase-7 precipitates with antiesterase-2 from the rabbit. 6. It differs from esterase-2 by its individual substrate preference and by its susceptibility to inhibition by acylating agents.     

Genetic diversity of populations of the earthworm Lumbricus rubellus (Hoffm.) (Oligochaeta, Lumbricidae)

The genetic diversity of Lumbricus rubellus Hoffm. earthworms collected in different parts of the Moscow and Kiev regions was studied by means of electrophoresis in polyacrylamide gel, using the loci encoding unspecific esterases and generic proteins as biochemical-genetic markers. A considerable diversity of samples in all alleles of these loci was revealed. With respect to allele frequencies of the locus My1, the samples from the Moscow and Kiev regions formed two genetically distinct spatial groups. Within these groups, the samples were genetically heterogeneous, and each of them could be regarded as an individual population.